Shedding light on disordered proteins Disordered proteins often fold as they bind to a partner protein. There could be many different molecular trajectories between the unbound proteins and the bound complex. Most methods to measure transition paths rely on monitoring a single distance, making it difficult to resolve complex pathways. Kim and Chung used fast three-color single-molecule Foster resonance energy transfer (FRET) to simultaneously probe distance changes between the two ends of an unfolded protein and between each end and a probe on the partner protein. They show that binding can be initiated by diverse conformations and that the molecules are held together by non-native interactions as the disordered protein folds. This allows the association to be diffusion limited because most collisions lead to binding. Science, this issue p. 1253 Three-color single-molecule Förster resonance energy transfer reveals diverse binding transition paths of disordered proteins. Transition paths of macromolecular conformational changes such as protein folding are predicted to be heterogeneous. However, experimental characterization of the diversity of transition paths is extremely challenging because it requires measuring more than one distance during individual transitions. In this work, we used fast three-color single-molecule Förster resonance energy transfer spectroscopy to obtain the distribution of binding transition paths of a disordered protein. About half of the transitions follow a path involving strong non-native electrostatic interactions, resulting in a transition time of 300 to 800 microseconds. The remaining half follow more diverse paths characterized by weaker electrostatic interactions and more than 10 times shorter transition path times. The chain flexibility and non-native interactions make diverse binding pathways possible, allowing disordered proteins to bind faster than folded proteins.

中文翻译：

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无序蛋白质在折叠并与伴侣结合时遵循不同的过渡路径

揭示无序蛋白质 无序蛋白质在与伴侣蛋白结合时通常会折叠。未结合的蛋白质和结合的复合物之间可能存在许多不同的分子轨迹。大多数测量过渡路径的方法都依赖于监测单个距离，因此很难解析复杂的路径。Kim 和 Chung 使用快速三色单分子福斯特共振能量转移 (FRET) 来同时探测未折叠蛋白两端之间以及每一端与伴侣蛋白上的探针之间的距离变化。他们表明结合可以由不同的构象引发，并且当无序蛋白质折叠时，分子通过非天然相互作用保持在一起。这允许关联受到扩散限制，因为大多数碰撞导致绑定。科学，这个问题 p。1253 三色单分子 Förster 共振能量转移揭示了无序蛋白质的多种结合转换路径。预测蛋白质折叠等大分子构象变化的过渡路径是异质的。然而，过渡路径多样性的实验表征极具挑战性，因为它需要在单个过渡期间测量多个距离。在这项工作中，我们使用快速三色单分子 Förster 共振能量转移光谱来获得无序蛋白质的结合跃迁路径的分布。大约一半的转换遵循涉及强非本机静电相互作用的路径，导致转换时间为 300 到 800 微秒。剩下的一半遵循更多样化的路径，其特征是静电相互作用较弱，过渡路径时间缩短 10 倍以上。链的灵活性和非天然相互作用使多种结合途径成为可能，使无序蛋白质比折叠蛋白质结合得更快。